Transcript The Periodic Table - Milton 7th Grade Advanced Science
The Periodic Table of the Elements
Basic Organization
Atomic structure is used to organize the elements in the periodic table.
Organized by atomic number
The periodic table is useful in predicting the chemical behavior, trends, and the properties on the elements.
3 basic categories:
Metals
Nonmetals
Metalloids
Atomic Structure Review
Atoms are made of protons , electrons , and neutrons.
Elements are atoms of only one type.
Elements number are identified by the atomic (# of protons in nucleus).
Energy Levels Review
Electrons are arranged in regions around the nucleus called energy levels.
At least 1 energy level and as many as 7 levels exist in atoms.
Electrons in levels farther away from the nucleus have more energy.
Inner levels will fill first before outer levels.
Energy Levels & Valence Electrons
Energy levels hold a specific amount of electrons:
1 st level = up to 2, 2 nd level = up to 8 3 rd level = up to18
The electrons in the outermost level are called valence electrons.
Determine how elements will react with others Outermost level does not usually fill completely with electrons.
Using the Table to Identify Valence Electrons
Elements are grouped because they have similar properties.
Group numbers can help you determine the number of valence electrons:
Group 1 has 1 valence electron.
Group 2 has 2 valence electrons.
Groups 3 – 12 are transition metals and have 1 or 2 valence electrons.
Using the Table to Identify Valence Electrons cont.
Groups 13 – 18 have 10 fewer than the group number. For example:
group 13 has 3 valence electrons
group 15 has 5 valence electrons
group 18 has 8 valence electrons
Grouping the Elements
The most reactive metals are the elements in Group 1 and 2. What makes an element reactive?
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Number of valence electrons each atom has
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When outer levels are full, atoms are stable When they are not full, they react: gain, lose, or share 1 or 2 electrons
Groups
Groups run vertically in the periodic table.
They are numbered from 1 – 18.
Elements in the same groups have the same number of electrons in the outer energy level.
Grouped elements behave chemically in similar ways.
Group 1: Alkali Metals
Contains: Metals
Valence Electrons: 1
Reactivity: Very Reactive
Properties:
solids
soft
react violently with water
shiny
low density
Group 2: Alkaline-Earth Metals
Contains: Metals
Valence Electrons: 2
Reactivity: very reactive but less reactive than alkali metals (Group 1)
Properties:
Solids
Silver colored
More dense than alkali metals
Groups 3-12 Transition Metals
Contain: Metals
Valence electrons: 1 or 2
Reactivity: less reactive than alkali and alkaline-earth metals
Properties:
Higher density
Good conductors of heat and electricity
Groups 3-12 Transition Metals Below Main Table
Contain: The Lanthanide and Actinide Series
These two rows are pulled out of sequence and placed below the main table to keep the table from being too wide.
Lanthanides are #’s 58 – 71.
Actinides are #’s 90 – 103.
Groups 3-12 Rare Earth Elements ~ Lanthanides
Lanthanides follow the transition metal # 57 Lanthanum in Period 6.
Valence electrons: 3 Reactivity: Very reactive Properties:
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High luster but tarnish easily High conductivity for electricity
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Very small differences between them
Groups 3-12 Rare Earth Elements ~ Actinides
Actinides follow the transition metal # 89 Actinium in Period 7 Valence electrons: 3 (but up to 6) Reactivity: unstable
All are radioactive
Most made in laboratories
Metalloids
A zig-zag line that separates metals from metalloids
Elements from Groups 13 – 17 contain some metalloids.
These elements have characteristics of metals and nonmetals.
Group 13: Boron Group
Group 13: Boron Group
Contains: 1 metalloid and 4 metals
Valence Electrons: 3
Reactivity: Reactive
Other shared properties:
Solid at room temperature
Group 14: Carbon Group
Contains: 1 non-metal, 2 metalloids, and 3 metals
Valence Electrons: 4
Reactivity: Varies
Other shared properties:
Solid at room temperature
Group 15: Nitrogen Group
Contains: 2 non-metals, 2 metalloids, and 1 metal
Valence electrons: 5
Reactivity: Varies
Other shared properties:
All but N are solid at room temperature
Group 16: Oxygen Group
Contains: 3 non-metals, 1 metalloid, and 2 metals
Valence Electrons: 6
Reactivity: Reactive
Other shared properties:
All but O are solid at room temperature.
Groups 17 : Halogens
Contain: Nonmetals
Valence Electrons: 7
Reactivity: Very reactive
Other shared properties
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Poor conductors of electric current
● ●
React violently with alkali metals to form salts Never found uncombined in nature
Group 18 Noble Gases
Contains: Nonmetals Valence Electrons: 8 (2 for He) Reactivity: Unreactive (least reactive group) Other shared properties:
Colorless, odorless gases at room temperature
Outermost energy level full All found in atmosphere
Hydrogen Stands Apart
H set apart because its properties don’t match any single group.
Valence electrons: 1
Reactivity: very but loses the 1 electron easily
Properties:
Similar to those of non-metals rather than metals
Periods
Periods run horizontally across the Periodic Table
Periods are numbered 1 – 7
All the elements in a period will have the same number of energy levels, which contain electrons. Examples:
Period 1 atoms have 1 energy level.
Period 2 atoms have 2 energy levels.
Period 5 atoms have 5 energy levels.
Periods continued
Moving across from left to right across a period, each element has one more electron in the outer shell of its atom than the element before it.
This leads to a fairly regular pattern of change in the chemical behavior of the elements across a period.